Add file version to .vik files.
Add map layer option to only download missing tiles.

Useful for low bandwidth and/or pay for data services yet you want the convenience of the autodownload.
Also useful for map types which hardly ever change e.g. BlueMarble,
 so no need to bother the server to ask if there are newer tiles!
Rework previous track layer option to Draw All Track Blacks into drawing in a specified colour.
Ensure when creating tracks they are allocated a colour.